How to prevent disconnect of a bluetooth device?

hello i have a problem with a bluetooth-keyboard. after i connect the keyboard it works well. if i leave the keyboard unused for a time it automatically disconnects. i think this is a feature that is set for security reasons but i’m not happy with it. i want to set up the connection that it stays permanent. i’m using plasma/kde. if you need further information please let me know.

Is your Bluetooth built-in or is it a USB dongle adapter that plugs into a USB port?